Title: Finned Tube With Vortex Generators For A Heat Exchanger.

Abstract

A system for and method of manufacturing a finned tube for a heat exchanger is disclosed herein. A continuous fin strip is provided with at one pair of vortex generators. A tube is rotated and linearly displaced while the continuous fin strip with vortex generators is spirally wrapped around the tube.

@article{osti_880547,
title = {Finned Tube With Vortex Generators For A Heat Exchanger.},
author = {Sohal, Manohar S. and O'Brien, James E.},
abstractNote = {A system for and method of manufacturing a finned tube for a heat exchanger is disclosed herein. A continuous fin strip is provided with at one pair of vortex generators. A tube is rotated and linearly displaced while the continuous fin strip with vortex generators is spirally wrapped around the tube.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2005,
month =
}

A system for and method of manufacturing a finned tube for a heat exchanger is disclosed herein. A continuous fin strip is provided with at least one pair of vortex generators. A tube is rotated and linearly displaced while the continuous fin strip with vortex generators is spirally wrapped around the tube.

A rod baffle is described comprising: parallel solid for hollow rods; at least some of these rods having longitudinal fins such that they have a cross-section of a serrated circle in at least some areas along the rod; the rods being arranged in the baffle to enable the engagement of the rods with adjacent elements; the rods being mounted as parallel chords across a generally circular support member to form the rod baffle.

Numerical investigations of three-dimensional flow and heat transfer in a finned tube with punched longitudinal vortex generators (LVG`s) are carried out for Reynolds number of 250 and 300. Air with a Prandtl number of 0.7 is used as the fluid. The flow is both thermally and hydrodynamically developing. The LVG is a delta winglet pair (DWP) punched out of the fin and is located directly behind the tube, symmetrically separated by one tube diameter. The DWP generates longitudinal vortices in the wake of the tube, defers flow separation on the tube, deflects the main stream into the tube wake, andmore » strong reduces the ``dead water zone.`` Heat transfer reversal is avoided by the DWP. Comparison of the span-averaged Nusselt numbers for the fin with and without DWP shows significant local heat transfer enhancement of several hundred percent in the tube wake. For Re = 300 and Fi = 200 the global heat transfer augmentation by a DWP, which amounts to only 2.5% of the fin area, is 31%.« less

A combined experimental and numerical investigation is under way to investigate heat transfer enhancement techniques that may be applicable to large-scale air-cooled condensers such as those used in geothermal power applications. The research is focused on whether air-side heat transfer can be improved through the use of finsurface vortex generators (winglets,) while maintaining low heat exchanger pressure drop. A transient heat transfer visualization and measurement technique has been employed in order to obtain detailed distributions of local heat transfer coefficients on model fin surfaces. Pressure drop measurements have also been acquired in a separate multiple-tube row apparatus. In addition, numericalmore » modeling techniques have been developed to allow prediction of local and average heat transfer for these low-Reynolds-number flows with and without winglets. Representative experimental and numerical results presented in this paper reveal quantitative details of local fin-surface heat transfer in the vicinity of a circular tube with a single delta winglet pair downstream of the cylinder. The winglets were triangular (delta) with a 1:2 height/length aspect ratio and a height equal to 90% of the channel height. Overall mean fin-surface Nusselt-number results indicate a significant level of heat transfer enhancement (average enhancement ratio 35%) associated with the deployment of the winglets with oval tubes. Pressure drop measurements have also been obtained for a variety of tube and winglet configurations using a single-channel flow apparatus that includes four tube rows in a staggered array. Comparisons of heat transfer and pressure drop results for the elliptical tube versus a circular tube with and without winglets are provided. Heat transfer and pressure-drop results have been obtained for flow Reynolds numbers based on channel height and mean flow velocity ranging from 700 to 6500.« less

A process is described for making a heat exchanger of aluminum, which consists of: applying a pattern of stop weld material to a first plate element; superimposing a second element on the first plate element and hot-rolling the plate elements together to form a plate; expanding the sides of the plate that are protected by the stop weld material by the application of fluid pressure to form a plurality of tubular heat exchanger medium flow passages; securing a plurality of fins by directed weld, without the use of foreign materials, at only one of their ends to the plate; holdingmore » a plurality of the plates in a frame; and securing the other end of each fin to the other part of a plate by applying additional fluid pressure with the tubular passages of sufficient magnitude to cause permanent deformation and metal-to-metal cohesive bonding between the other end and the surface of the plate.« less